Methods for supplying, filling and sealing at high speed are gradually spreading among the industrial world in order to increase the production speed of a package in a work of packaging an item to be packaged such as edible processed products (e.g., fish meat and ham, sausage), dairy products (e.g., cheese and butter) and liquid soups for ready-to-eat foods. Examples of the methods include a method in which a plastic film is continuously fed to form a packaging bag at high speed, and almost simultaneously, an item to be packaged is supplied into a packaging bag in a vertical direction, and the item is filled in the bag, and the bag is sealed, by using a vertical form fill seal machine (VFFS) (e.g., Patent documents 1 and 2). In the method of high speed packaging by using VFFS, the item to be packaged falls in a vertical direction onto a lower seal portion directly after heat sealing in which the lower seal portion is not sufficiently cooled. Accordingly, there is a possibility that the bag is broken with tearing of a lower sealed face when the item to be packaged falls, for example, if the item is heavy or if the shape of item includes a projection. For preventing such defect, there are two main performances required for a heat-sealable layer. One is high heat sealability (i.e., a performance of manifesting high heat sealing strength even if the sealing temperature is lower than a current sealing temperature, or manifesting high heat sealing strength even if the sealing time is short while the sealing temperature is a current sealing temperature). Another one is high hot tack (i.e., a performance of manifesting high adhesion of a sealed portion even if the sealed portion is not sufficiently cooled down and it is still in a high temperature state after heat sealing. In this field, resin films based on a linear low density polyethylene (L-LDPE) have been widely used heretofore. However, needs have been grown to provide a laminated film having more excellent heat sealability and hot tack for use in high speed packaging in order to conform to a further increased filling and sealing speed.